There have been some reports of people with totally dead Macs after running OS X. The causes seem very hard to pin down, but the common condition of the machines is an inability to boot off of a OS 9 CD. The machine is stuck running OS X, despite everything the user tries to fix the problem (including booting into open firmware, resetting parameter RAM, setting the system disk, etc.).

One final thing to try is turn the machine off, open it up, and pull the battery out of the motherboard. Wait a decent amount of time (five minutes or more), reinsert the battery, and restart. This should force your machine to forget about anything it thinks it knows, and go back to the factory configuration. Your CD drive should now boot the machine (when holding down 'C' during boot). I've seen reports of this working for more than one person, but there have been a couple poor souls that have tried this and are still non-functional.

I had this - could not boot off OS 9 CD ROM, could not boot OS X or OS 9, and could not
reinstall X from OS X CD ROM!!!!

For the record, I got the error: "Code fragment could not be completed" from the OS 9 boot
sequence which I have never, ever seen before in 13 years of Mac use!! Woohoo!

Here's my fix:

Put your OS 9 CD in. startup and zap the P-RAM (or NVRAM) with option-command-P-R on
startup. Zap it a couple of times and then, when it is restarting, hold down C and it should
boot from the CD ROM. If not, try another few zaps and hold down C. IF you try to boot into
OS 9, it will fail, and then the CD ROM boot will also fail. The CD ROM boot attempt must
come directly after zapping the NVRAM.

Once in the OS 9 CD, I backep up and reformatted all my drives, but I'm pretty sure a clean
install of the system would fix the problems for OS 9. I'm also pretty sure that re-installing
OS X will fail (it did for me) so tar up and pull off /Users and /Applications to somewhere
else, reformat, reinstall X and overlay the Applications dirs. You'll have to recreate all the
users, but then you can overly /Users (although I didn't - I only overlaid /Users/username/*

Also, my Entrega USB card no longer works under OS 9 despite reinstalling the drivers - but
it works under OS X!!!

I had the same problem a couple days ago...
I installed a new and bigger hard disk in my [original] iBook. I did a full install of Mac OS
9.0.4 on the first partition and only had a problem with "Automatic Update Software" crashing
my machine. I fixed that problem and then installed Mac OS X PB and dev tools.
Everything worked OK but I couldn't reboot in Mac OS 9. I tried from a CD and it didn't work.
After a while my iBook refused to boot from the CD or HD.

I zapped the PRAM (NVRAM) about ten times with the CD installed in the iBook [rebooted
with "C" pressed] and it did the trick.

I ran Disk First Aid 8.6 and it reported that both of my partitions had "wrappers" errors
[described on macfixit.com and macintouch.com pages].

After the partitions were repaired I had no problem switching back and forth between Mac OS
9 and Mac OS X PB.

I just formatted (zeroing out the data) my drive and reinstalled both OSX and OS9.1 (on seperate partitions this time). On my first boot, I got the blinking question mark after I had installed 9.1. After I zapped the pram a few times it booted. Now it appears that both system's work fine. We'll see.

Another way to live again with macosx
Authored by: Daryopik on Nov 24, '01 10:00:44AM

I had the same problem.. the machine was dead... that orrible blue screen was facing me with a static expression :). I wasn't able to boot from CD... and from OS9 neither..
BUT i when i thought that maybe the solution was destroy everything in the HD, i had a brilliant idea that helped me to make my os-x live AGAIN.
I opened the Mac then i've disconnected the HD so i forced the mac to boot from CD. Then i, when i started the mac with mac os9.2.1, i choose as startup disc the CD.
Then i shut down and re- connected the HD.. Started again the mac (from cd obvioulsy) i was able to see my HD.. Yahhhoooooo (not the website :) ).. then choose from the contol panel "start up disc" and i selected MY HD (not osx system but classic os9) as start up disk (if you don'y have os9 installed use the cd to install it :) ).
Then i restarted the mac. It started again from the HD!!!!!
Then .... then you have to choose what to do.. if delete osx and reinstall it or try to reinstall it on the old osx.. anyway your mac is living again and soon with osx..... :)
Thanks
Dario